Dents in sheet metal, as for example in the body of an automobile, are usually flattened by means of a two-stage operation. First the dent is pulled out from its concave side or hammered out from its convex side until it assumes a position slightly below that position which it had before the dent was formed. Thereafter the dented region is filled and this filler is sanded and smoothed out.
This operation is relatively costly, as it demands the careful work of skilled personnel. Furthermore such a process leaves stresses in the metal which make the repaired region readily deformable.